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array: safer implementation of try_create_array

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This commit is contained in:
David Hewitt 2021-04-24 08:42:44 +01:00
parent 9bc5089e4b
commit 7ead166d9d
4 changed files with 93 additions and 105 deletions
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2
CHANGELOG.md
View file

@ -13,7 +13,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/spec/v2.0.0.
- Support PyPy 3.7. [#1538](https://github.com/PyO3/pyo3/pull/1538)
### Added
- Add conversion for `[T; N]` for all `N` on Rust 1.51 and up. [#1128](https://github.com/PyO3/pyo3/pull/1128)
- Add conversions for `[T; N]` for all `N` on Rust 1.51 and up. [#1128](https://github.com/PyO3/pyo3/pull/1128)
- Add conversions between `OsStr`/`OsString`/`Path`/`PathBuf` and Python strings. [#1379](https://github.com/PyO3/pyo3/pull/1379)
- Add `#[pyo3(from_py_with = "...")]` attribute for function arguments and struct fields to override the default from-Python conversion. [#1411](https://github.com/PyO3/pyo3/pull/1411)
- Add FFI definition `PyCFunction_CheckExact` for Python 3.9 and later. [#1425](https://github.com/PyO3/pyo3/pull/1425)

187
src/conversions/array.rs
View file

@ -1,9 +1,21 @@
use crate::{FromPyObject, IntoPy, PyAny, PyObject, PyResult, PyTryFrom, Python, ToPyObject};
use crate::{
exceptions, FromPyObject, IntoPy, PyAny, PyErr, PyObject, PyResult, PyTryFrom, Python,
ToPyObject,
};
#[cfg(not(min_const_generics))]
macro_rules! array_impls {
($($N:expr),+) => {
$(
impl<T> IntoPy<PyObject> for [T; $N]
where
T: ToPyObject
{
fn into_py(self, py: Python) -> PyObject {
self.as_ref().to_object(py)
}
}
impl<'a, T> FromPyObject<'a> for [T; $N]
where
T: Copy + Default + FromPyObject<'a>,
@ -55,6 +67,16 @@ array_impls!(
26, 27, 28, 29, 30, 31, 32
);
#[cfg(min_const_generics)]
impl<T, const N: usize> IntoPy<PyObject> for [T; N]
where
T: ToPyObject,
{
fn into_py(self, py: Python) -> PyObject {
self.as_ref().to_object(py)
}
}
#[cfg(min_const_generics)]
impl<'a, T, const N: usize> FromPyObject<'a> for [T; N]
where
@ -71,60 +93,27 @@ where
}
}
#[cfg(not(min_const_generics))]
macro_rules! array_impls {
($($N:expr),+) => {
$(
impl<T> IntoPy<PyObject> for [T; $N]
where
T: ToPyObject
{
fn into_py(self, py: Python) -> PyObject {
self.as_ref().to_object(py)
}
}
)+
}
}
#[cfg(not(min_const_generics))]
array_impls!(
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25,
26, 27, 28, 29, 30, 31, 32
);
#[cfg(min_const_generics)]
impl<T, const N: usize> IntoPy<PyObject> for [T; N]
where
T: ToPyObject,
{
fn into_py(self, py: Python) -> PyObject {
self.as_ref().to_object(py)
}
}
#[cfg(all(min_const_generics, feature = "nightly"))]
impl<'source, T, const N: usize> FromPyObject<'source> for [T; N]
where
for<'a> T: FromPyObject<'a> + crate::buffer::Element,
for<'a> T: Default + FromPyObject<'a> + crate::buffer::Element,
{
fn extract(obj: &'source PyAny) -> PyResult<Self> {
let mut array: core::mem::MaybeUninit<[T; N]> = core::mem::MaybeUninit::uninit();
use crate::{AsPyPointer, PyNativeType};
let mut array = [T::default(); N];
// first try buffer protocol
if unsafe { crate::ffi::PyObject_CheckBuffer(obj.as_ptr()) } == 1 {
if let Ok(buf) = crate::buffer::PyBuffer::get(obj) {
if buf.dimensions() == 1 && buf.copy_to_slice(obj.py(), &mut array).is_ok() {
buf.release(obj.py());
// SAFETY: The array should be fully filled by `copy_to_slice`
return Ok(unsafe { array.assume_init() });
return Ok(array);
}
buf.release(obj.py());
}
}
// fall back to sequence protocol
_extract_sequence_into_slice(obj, &mut array)?;
// SAFETY: The array should be fully filled by `_extract_sequence_into_slice`
Ok(unsafe { array.assume_init() })
Ok(array)
}
}
@ -135,14 +124,56 @@ where
{
let seq = <crate::types::PySequence as PyTryFrom>::try_from(obj)?;
let expected_len = seq.len()? as usize;
let mut counter = 0;
try_create_array(&mut counter, |idx| {
array_try_from_fn(|idx| {
seq.get_item(idx as isize)
.map_err(|_| crate::utils::invalid_sequence_length(expected_len, idx + 1))?
.map_err(|_| invalid_sequence_length(expected_len, idx + 1))?
.extract::<T>()
})
}
// TODO use std::array::try_from_fn, if that stabilises:
// (https://github.com/rust-lang/rust/pull/75644)
#[cfg(min_const_generics)]
fn array_try_from_fn<E, F, T, const N: usize>(mut cb: F) -> Result<[T; N], E>
where
F: FnMut(usize) -> Result<T, E>,
{
// Helper to safely create arrays since the standard library doesn't
// provide one yet. Shouldn't be necessary in the future.
struct ArrayGuard<T, const N: usize> {
dst: *mut T,
initialized: usize,
}
impl<T, const N: usize> Drop for ArrayGuard<T, N> {
fn drop(&mut self) {
debug_assert!(self.initialized <= N);
let initialized_part = core::ptr::slice_from_raw_parts_mut(self.dst, self.initialized);
unsafe {
core::ptr::drop_in_place(initialized_part);
}
}
}
// [MaybeUninit<T>; N] would be "nicer" but is actually difficult to create - there are nightly
// APIs which would make this easier.
let mut array: core::mem::MaybeUninit<[T; N]> = core::mem::MaybeUninit::uninit();
let mut guard: ArrayGuard<T, N> = ArrayGuard {
dst: array.as_mut_ptr() as _,
initialized: 0,
};
unsafe {
let mut value_ptr = array.as_mut_ptr() as *mut T;
for i in 0..N {
core::ptr::write(value_ptr, cb(i)?);
value_ptr = value_ptr.offset(1);
guard.initialized += 1;
}
core::mem::forget(guard);
Ok(array.assume_init())
}
}
fn _extract_sequence_into_slice<'s, T>(obj: &'s PyAny, slice: &mut [T]) -> PyResult<()>
where
T: FromPyObject<'s>,
@ -150,10 +181,7 @@ where
let seq = <crate::types::PySequence as PyTryFrom>::try_from(obj)?;
let expected_len = seq.len()? as usize;
if expected_len != slice.len() {
return Err(crate::utils::invalid_sequence_length(
expected_len,
slice.len(),
));
return Err(invalid_sequence_length(expected_len, slice.len()));
}
for (value, item) in slice.iter_mut().zip(seq.iter()?) {
*value = item?.extract::<T>()?;
@ -161,41 +189,11 @@ where
Ok(())
}
#[cfg(min_const_generics)]
fn try_create_array<E, F, T, const N: usize>(counter: &mut usize, mut cb: F) -> Result<[T; N], E>
where
F: FnMut(usize) -> Result<T, E>,
{
// Helper to safely create arrays since the standard library doesn't
// provide one yet. Shouldn't be necessary in the future.
struct ArrayGuard<'a, T, const N: usize> {
dst: *mut T,
initialized: &'a mut usize,
}
impl<T, const N: usize> Drop for ArrayGuard<'_, T, N> {
fn drop(&mut self) {
debug_assert!(*self.initialized <= N);
let initialized_part = core::ptr::slice_from_raw_parts_mut(self.dst, *self.initialized);
unsafe {
core::ptr::drop_in_place(initialized_part);
}
}
}
let mut array: core::mem::MaybeUninit<[T; N]> = core::mem::MaybeUninit::uninit();
let guard: ArrayGuard<T, N> = ArrayGuard {
dst: array.as_mut_ptr() as _,
initialized: counter,
};
unsafe {
for (idx, value_ptr) in (&mut *array.as_mut_ptr()).iter_mut().enumerate() {
core::ptr::write(value_ptr, cb(idx)?);
*guard.initialized += 1;
}
core::mem::forget(guard);
Ok(array.assume_init())
}
pub fn invalid_sequence_length(expected: usize, actual: usize) -> PyErr {
exceptions::PyValueError::new_err(format!(
"expected a sequence of length {} (got {})",
expected, actual
))
}
#[cfg(test)]
@ -204,33 +202,32 @@ mod test {
#[cfg(min_const_generics)]
use std::{
panic,
sync::{Arc, Mutex},
thread::sleep,
time,
sync::atomic::{AtomicUsize, Ordering},
};
#[cfg(min_const_generics)]
#[test]
fn try_create_array() {
#[allow(clippy::mutex_atomic)]
let counter = Arc::new(Mutex::new(0));
let counter_unwind = Arc::clone(&counter);
fn array_try_from_fn() {
static DROP_COUNTER: AtomicUsize = AtomicUsize::new(0);
struct CountDrop;
impl Drop for CountDrop {
fn drop(&mut self) {
DROP_COUNTER.fetch_add(1, Ordering::SeqCst);
}
}
let _ = catch_unwind_silent(move || {
let mut locked = counter_unwind.lock().unwrap();
let _: Result<[i32; 4], _> = super::try_create_array(&mut *locked, |idx| {
let _: Result<[CountDrop; 4], ()> = super::array_try_from_fn(|idx| {
if idx == 2 {
panic!("peek a boo");
}
Ok::<_, ()>(1)
Ok(CountDrop)
});
});
sleep(time::Duration::from_secs(2));
assert_eq!(*counter.lock().unwrap_err().into_inner(), 2);
assert_eq!(DROP_COUNTER.load(Ordering::SeqCst), 2);
}
#[cfg(not(min_const_generics))]
#[test]
fn test_extract_bytearray_to_array() {
fn test_extract_small_bytearray_to_array() {
let gil = Python::acquire_gil();
let py = gil.python();
let v: [u8; 3] = py

1
src/lib.rs
View file

@ -186,7 +186,6 @@ pub mod pyclass_slots;
mod python;
pub mod type_object;
pub mod types;
mod utils;
#[cfg(feature = "serde")]
pub mod serde;

8
src/utils.rs
View file

@ -1,8 +0,0 @@
use crate::{exceptions, PyErr};
pub fn invalid_sequence_length(expected: usize, actual: usize) -> PyErr {
exceptions::PyValueError::new_err(format!(
"expected a sequence of length {} (got {})",
expected, actual
))
}